This invention relates to a steering actuator, and more particularly, this invention relates to a steering actuator capable of providing variable ratio steering, variable steering force feedback, and driver transparent autonomous steering.
Steering systems function to assist a vehicle operator in directing the road wheels in order to steer the vehicle. In conventional steering systems, the operator controls the direction of the vehicle with the aid of a hand wheel mechanically connected to the road wheels.
Rack and pinion steering has become a common type of steering on vehicles. In a typical example, a pinion gear is attached to the steering shaft of a steering wheel. When the steering wheel is turned by the operator, the pinion gear spins which moves a rack. Connected to each end of the rack is a tie rod which is connected in some fashion to the wheels of the vehicle. Thus, the rack and pinion system converts the rotational motion of the steering wheel into linear motion which turns the wheels of the vehicle.
Some vehicles employ variable ratio steering which utilize a different number of teeth per inch in the center of the rack than on an outer portion of the rack. In effect, varying the number of teeth per inch can allow a manufacturer of a vehicle to embrace desired advantages, such as allowing the vehicle to responds quickly at the outset of a turn when the rack is near the center and reducing driver effort near the wheel""s turning limits.
The steering actuator system includes a driver feedback rack for receiving input from a steering wheel, a vehicle steering rack, separate from the driver feedback rack, and a variable feedback device connecting the driver feedback rack to the vehicle steering rack, wherein linear motion of the driver feedback rack is translated to variable linear motion of the vehicle steering rack through the variable feedback device.